What is the interquartile range of this data set - 5,-4,-3,-2,-1,0,1,2,3,4,5,7,7,7

IQR=5+2=7 because you have to find the median and the median below the median and above the median to get 5 and a negative two and 5 subtract a negative is the same as adding a positive so then you get 7.